This invention relates to power supplies. In particular it relates to modular construction of power supplies.
By separating a power supply into functional circuit elements and fabricating and testing these elements prior to final assembly of the supply, a manufacturer can save on labor and material waste costs while also increasing reliability. A power supply circuit element that particularly lends itself to such modularization is a voltage multiplier.
A voltage multiplier is a circuit element that accepts a low level ac voltage as an input and yields a high level d.c. voltage as an output. Fabricating and testing miniaturized voltage multipliers has traditionally proved to be a very costly endeavor because miniature high voltage components, such as voltage multipliers, cannot be tested in free air. The close proximity of the low voltage input circuitry and the high voltage output circuitry causes destructive input-to-output arc-over to take place. Arc-over can only be avoided by completely immersing the multiplier in a substantially non-conductive material before powering its circuits.
A common solution to testing this problem is to fabricate the multiplier circuit, insert it into an isolated compartment (defined by rigid walls) in the power supply encasement where the multiplier is to be used, affix it into place by filling (or potting) the compartment with a substantially non-conductive compound, and then test the multiplier. This approach is very costly since if a multiplier proves to be defective upon testing, the entire power supply encasement must be discarded, thereby creating a substantial waste of labor and materials.
Voltage multipliers designed for use in toroidally shaped miniature power supplies have an additional fabrication problem. Generally, such multipliers are initially assembled on a planar, flexible circuit board. Each multiplier, prior to being affixed into the power supply encasement, must be bent into a cylindrical section so that its curvature substantially matches that of the interior surface of the toroidal power supply encasement. This enables the region that the multiplier occupies inside the encasement to be as small as possible. There is a risk that this bending will cause fragile interconnections in the multiplier circuitry to break. Often these failures are not detectable until the multiplier is tested after it is affixed within the power supply encasement, at which point the entire encasement must be discarded.
Another conventional approach is to bend the multiplier and then to submerse it in a non-conductive liquid during the testing phase. The multiplier, once tested, is then affixed into place as described above and retested. This approach also has substantial risk of waste because affixing the multiplier into place, even unaccompanied by bending, is often enough to cause fragile, exposed interconnections in the multiplier circuit to become detached. By the time these failures are discovered, the multiplier has once again been affixed within the encasement, thus requiring the encasement to be discarded.
Aside from waste costs incurred during the testing of the voltage multipliers, conventional approaches also suffer from reliability problems. In the prior art, once a potted circuit element, such as a voltage multiplier, has been affixed into an isolated compartment in a power supply encasement and tested, the remainder of the encasement is filled with circuitry, tested, and then filled with a similar non-conductive compound used in the multiplier compartment. Often only a frictional bond can be achieved between the walls which define the isolated compartments and the non-conductive compounds used to affix the power supply elements into place. Therefore, interfaces between the compounds and the walls of the compartments (where the multiplier and other like circuitry reside) have proven to be a source of moisture seepage, which may result in arc-over at the respective interfaces. The probability of failure due to moisture seeping into the power supply would be substantially reduced when these interfaces are eliminated.
In addition to reliability problems, the walls of the isolated compartments take up valuable space that could otherwise be used for circuitry.
Accordingly, it is the object of the present invention to provide an improved modular power supply. It is another object to provide an improved modular power supply whereby circuit elements, such as voltage multipliers, can be fabricated, encapsulated and then tested in free air prior to being installed into the power supply encasement, thereby substantially reducing the labor and material waste costs associated with the manufacturing of power supplies.
It is also an object of this invention to eliminate the need for well-defined, isolated compartments inside a power supply encasement, thereby eliminating interfaces that are a proven source of moisture seepage and circuit failure, and also providing a substantial space savings.
It is a further object of the invention to provide a modular power supply structure specifically for applications in toroidally shaped power supplies.